Dolerite. The chemical composition of seepage wate r sampled at the A2-B21 boundary of MN8 . The essential minerals are plagioclase feldspar and pyroxene, which together constitute between about 60% and 80% of the total rock composition. Diabase is usually found in smaller relatively shallow intrusive bodies such as dikes and sills. Picritic dolerite: At least 50/6 of the rock is composed of olivine. [13] Large dolerite sills such as the Golden Mile Dolerite can exhibit coarse-grained texture, and show a large diversity in petrography and geochemistry across the width of the sill.[14]. A total of 16 dikes of both compositions were studied and samples collected for geochemical and petrographical analysis. Total . & Barton, M.: Major element chemistry of Precambrian dolerite dikes of tholeiitic composition from Rogaland/Vest Agder, SW Norway. See more. Diabase is the preferred name in North America, while dolerite is the preferred name in the rest of English-speaking world, where sometimes the name diabase is applied to altered dolerites and basalts. This diabasic texture is also termed interstitial. Like other mafic rocks, it is relatively low in silica content. Alteration of primary minerals Chlorite Several chlorite crystals from the meta-dolerite parent material were analysed on the electron microprobe and their chemical composition (Table I) corresponds to the structural formula: (Mg2.40 Fe2+2.26 Al~. Sr . There are often traces of other minerals such as iron and copper pyrites. Dolerite, also called diabase, is a dark igneous rock intermediate in grain size between basalt and gabbro.Consisting of plagioclase feldspar and pyroxene, it is a widespread intrusive rock, quarried for crushed and monumental stone (known as "black granite").. formation. It typically forms slabs and blocks and the varying crystal size and exact chemical make-up determines its roughness. Chemical composition. The essential minerals are plagioclase feldspar and pyroxene, which together constitute between about 60% and 80% of the total rock composition. During this process, the ferromagnesian minerals weather chemically, releasing iron and magnesium which recrystallise to form iron-rich montmonllomte In the fine-clay fraction. C: Doleritic texture with plagioclase, apatite, feldspar and Fe-Ti oxides phenocrysts with clinopyroxene oikocryst (MK2). Diabase also serves as local building stone. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine grained to aphanitic chilled margins which may contain tachylite (dark mafic glass). [17][18], Diabase is crushed and used as a construction aggregate for road beds, buildings, railroad beds (rail ballast), and within dams and levees. As may be inferred from their highly crystalline state they are very often intrusive, and … Dolerite is composed of two essential and several accessory minerals. Diabase or Dolerite Diabase or dolerite is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. The soils form a sequence ranging from a Black Vertosol (P8) to four texture contrast soils namely a Eutrophic Brown Chromosol (P5), two Mottled-Subnatric Grey Sodosols [4] It is also abundant in large parts of Curaçao, an island off the coast of Venezuela. In the Thuringian-Franconian-Vogtland Slate Mountains of central Germany the diabase is entirely of Devonian age. It can include. The dikes are vertical or nearly so and strike approximately N40° W. Three major northeast-trending faults also occur in the study area. Intrusive rocks such as por-phyritic granite, gabbro and dolerite are found as concordant and discordant intrusions within CGC. 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